Quantum and transport lifetimes due to roughness-induced scattering of a two-dimensional electron gas in wurtzite group-III-nitride heterostructures

Abstract

A theory is presented of the quantum and transport lifetimes of the two-dimensional electron gas (2DEG) at low temperature in a uniformly doped wurtzite group-III-nitride single heterostructure. In the calculation, besides the well-known scattering mechanisms, we took into account the roughness-induced scatterings, viz. misfit piezoelectric charges and misfit deformation potential. We proved that these exhibit important scattering sources for the 2DEG in wurtzite group-III-nitride heterostructures, in particular, the piezoelectric charges and alloy disorder dominate the transport and quantum lifetimes in a high-density regime (e.g., ${n}_{s}=2\ifmmode\times\else\texttimes\fi{}{10}^{12}--10\ifmmode\times\else\texttimes\fi{}{10}^{12}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$). Further, it is found that because of uniform doping, the electron distribution may be remarkably shifted far away from the key scattering sources, thus increasing the lifetimes. Our theory is able to provide a good quantitative explanation of the recent experimental data about the 2DEG lifetimes in a background-doped ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}∕\mathrm{Ga}\mathrm{N}$ heterostructure. The theory may reproduce not only the magnitude but also the nonmonotonic (bell-shaped) dependencies on the carrier density of both the transport and quantum lifetimes as well as their ratio, which could not be understood if starting merely from the scattering mechanisms known so far.